Strange Particle Production In PP Collisions

Under laboratory conditions,the collision of two high-energy heavy ion beams can generate a new state of matter with high temperature and density called QuarkGluon Plasma(QGP).Research on the properties of QGP has always been at the forefront of high-energy nuclear physics.Traditionally,small system collisions(p-p,p-Pb)are used as a reference for studying the QGP properties in heavy ion collisions(large systems).However,recently observed new physical phenomena in small systems,such as enhanced production of strange baryons-mesons ratios and fow-like collectivities which QGP-like signals,have led to a re-examination of the conditions of the QGP formation.Therefore,studying the production mechanisms of strange hadrons in small systems is of great signifcance for explaining the QGP-like signals observed in small system collisions.The studies in proton-proton collisions have found that the color reconnection based on string fragmentation can describe well the experimental observation of the enhanced Λ+c/D0 hadron-meson yield ratio.However,there is a signifcant discrepancy between the color reconnection prediction and the experimental observation on the strange charmed baryons Ξ+cand ?0c.Moreover,the discrepancy which increases with the strangeness.On the other hand,the color reconnection also underestimates the strange hadrons composed of light quarks,and the underestimation increases with the strangeness.These phenomena indicate that the color reconnection based on string fragmentation cannot well describe the production of strange hadrons.Under this context,this work aims to study the production mechanism of strange hadrons in small system collisions through the hadronization of string fragmentation using the PYTHIA8 and various evolution stages in a multi-phase transport model based on the PYTHIA8 initial conditions.This article is divided into three parts: the motivation,the background of the study,and results and discussions.The motivation introduces the Standard Model,the strong interaction,the QGP,and the current research status of the QGP-like signal in small systems.The background introduces the two phenomenological models,PYTHIA8 and a multi-phase transport model based on the PYTHIA8 initial conditions,which are used in this work.The physical principles of the Lund string fragmentation and color reconnection mechanisms in the PYTHIA8,as well as parton cascade,the quark coalescence,and hadron cascade and decay processes in a multiphase transport model based on PYTHIA8 initial conditions are emphasized.The results and discussions conclude the following: 1.The hadronization via Lund string fragmentation in PYTHIA8 is not able to build a simultaneous description of the production of all strange hadrons species,and the yield of various strange hadrons is insensitive to the probability of having a strange quark in one of the diquarks at the endpoint of the newly formed string.2.The key to resolving the issue of the relative overestimation of the simulated strange baryon-to-meson ratio at high transverse momentum in comparison to experimental results lies in determining whether the hadron rescattering cross section of the reaction channel related to Λ + ˉΛ in the hadron cascade is correctly modeled and whether the contribution of the decay of excited states to the yield of the fnal state Λ + ˉΛ is accurately estimated.3.The production of multi-strange hadrons is not dependent on a single hadronization mechanism,and the quark coalescence mechanisms is of great signifcance for understanding the production of multi-strange hadrons in proton-proton collisions.4.The production of multi-strange hadrons in small systems may originate from the contributions of both the quark coalescence and hadron cascade mechanisms.